.\"
.\" Sun Microsystems, Inc. gratefully acknowledges The Open Group for
.\" permission to reproduce portions of its copyrighted documentation.
.\" Original documentation from The Open Group can be obtained online at
.\" http://www.opengroup.org/bookstore/.
.\"
.\" The Institute of Electrical and Electronics Engineers and The Open
.\" Group, have given us permission to reprint portions of their
.\" documentation.
.\"
.\" In the following statement, the phrase ``this text'' refers to portions
.\" of the system documentation.
.\"
.\" Portions of this text are reprinted and reproduced in electronic form
.\" in the SunOS Reference Manual, from IEEE Std 1003.1, 2004 Edition,
.\" Standard for Information Technology -- Portable Operating System
.\" Interface (POSIX), The Open Group Base Specifications Issue 6,
.\" Copyright (C) 2001-2004 by the Institute of Electrical and Electronics
.\" Engineers, Inc and The Open Group.  In the event of any discrepancy
.\" between these versions and the original IEEE and The Open Group
.\" Standard, the original IEEE and The Open Group Standard is the referee
.\" document.  The original Standard can be obtained online at
.\" http://www.opengroup.org/unix/online.html.
.\"
.\" This notice shall appear on any product containing this material.
.\"
.\" The contents of this file are subject to the terms of the
.\" Common Development and Distribution License (the "License").
.\" You may not use this file except in compliance with the License.
.\"
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
.\" or http://www.opensolaris.org/os/licensing.
.\" See the License for the specific language governing permissions
.\" and limitations under the License.
.\"
.\" When distributing Covered Code, include this CDDL HEADER in each
.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
.\" If applicable, add the following below this CDDL HEADER, with the
.\" fields enclosed by brackets "[]" replaced with your own identifying
.\" information: Portions Copyright [yyyy] [name of copyright owner]
.\"
.\"
.\" Portions Copyright (c) 1992, X/Open Company Limited.  All Rights Reserved.
.\" Copyright (c) 2003, Sun Microsystems, Inc.  All Rights Reserved.
.\"
.TH MSGSND 2 "Feb 11, 2003"
.SH NAME
msgsnd \- message send operation
.SH SYNOPSIS
.LP
.nf
#include <sys/msg.h>

\fBint\fR \fBmsgsnd\fR(\fBint\fR \fImsqid\fR, \fBconst void *\fR\fImsgp\fR, \fBsize_t\fR \fImsgsz\fR, \fBint\fR \fImsgflg\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBmsgsnd()\fR function is used to send a message to the queue associated
with the message queue identifier specified by \fImsqid\fR.
.sp
.LP
The \fImsgp\fR argument points to a user-defined buffer that must contain first
a field of type \fBlong int\fR that will specify the type of the message, and
then a data portion that will hold the data bytes of the message. The structure
below is an example of what this user-defined buffer might look like:
.sp
.in +2
.nf
struct  mymsg {
        long  mtype;     /* message type */
        char  mtext[1];  /* message text */
}
.fi
.in -2

.sp
.LP
The \fBmtype\fR member is a non-zero positive type \fBlong int\fR that can be
used by the receiving process for message selection.
.sp
.LP
The \fBmtext\fR member is any text of length \fImsgsz\fR bytes. The \fImsgsz\fR
argument can range from 0 to a system-imposed maximum.
.sp
.LP
The \fImsgflg\fR argument specifies the action to be taken if one or more of
the following are true:
.RS +4
.TP
.ie t \(bu
.el o
The number of bytes already on the queue is equal to \fBmsg_qbytes\fR. See
\fBIntro\fR(2).
.RE
.RS +4
.TP
.ie t \(bu
.el o
The total number of messages on the queue would exceed the maximum allowed by
the system. See NOTES.
.RE
.sp
.LP
These actions are as follows:
.RS +4
.TP
.ie t \(bu
.el o
If (\fImsgflg\fR\fB&IPC_NOWAIT\fR) is non-zero, the message will not be sent
and the calling process will return immediately.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If (\fImsgflg\fR\fB&IPC_NOWAIT\fR) is 0, the calling process will suspend
execution until one of the following occurs:
.RS +4
.TP
.ie t \(bu
.el o
The condition responsible for the suspension no longer exists, in which case
the message is sent.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The message queue identifier \fImsqid\fR is removed from the system (see
\fBmsgctl\fR(2)); when this occurs, \fBerrno\fR is set equal to \fBEIDRM\fR and
\fB\(mi1\fR is returned.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The calling process receives a signal that is to be caught; in this case the
message is not sent and the calling process resumes execution in the manner
prescribed in \fBsigaction\fR(2).
.RE
.RE
.sp
.LP
Upon successful completion, the following actions are taken with respect to the
data structure associated with \fImsqid\fR (see \fBIntro\fR(2)):
.RS +4
.TP
.ie t \(bu
.el o
\fBmsg_qnum\fR is incremented by 1.
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fBmsg_lspid\fR is set equal to the process \fBID\fR of the calling process.
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fBmsg_stime\fR is set equal to the current time.
.RE
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is
returned, no message is sent, and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBmsgsnd()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEACCES\fR\fR
.ad
.RS 10n
Operation permission is denied to the calling process. See \fBIntro\fR(2).
.RE

.sp
.ne 2
.na
\fB\fBEAGAIN\fR\fR
.ad
.RS 10n
The message cannot be sent for one of the reasons cited above and
(\fImsgflg\fR\fB&IPC_NOWAIT\fR) is non-zero.
.RE

.sp
.ne 2
.na
\fB\fBEIDRM\fR\fR
.ad
.RS 10n
The message queue identifier \fImsgid\fR is removed from the system.
.RE

.sp
.ne 2
.na
\fB\fBEINTR\fR\fR
.ad
.RS 10n
The \fBmsgsnd()\fR function was interrupted by a signal.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value of \fImsqid\fR is not a valid message queue identifier, or the value
of \fBmtype\fR is less than 1.
.sp
The value of \fImsgsz\fR is less than 0 or greater than the system-imposed
limit.
.RE

.sp
.LP
The \fBmsgsnd()\fR function may fail if:
.sp
.ne 2
.na
\fB \fBEFAULT\fR\fR
.ad
.RS 11n
The \fImsgp\fR argument points to an illegal address.
.RE

.SH USAGE
.sp
.LP
The value passed as the \fImsgp\fR argument should be converted to type \fBvoid
*\fR.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
.BR Intro (2),
.BR msgctl (2),
.BR msgget (2),
.BR msgrcv (2),
.BR setrctl (2),
.BR sigaction (2),
.BR attributes (7),
.BR standards (7),
.BR rctladm (8)
.SH NOTES
.sp
.LP
The maximum number of messages allowed on a message queue is the minimum
enforced value of the \fBprocess.max-msg-messages\fR resource control of the
creating process at the time \fBmsgget\fR(2) was used to allocate the queue.
.sp
.LP
 See \fBrctladm\fR(8) and \fBsetrctl\fR(2) for information about using
resource controls.
